Name: ____________________________
Science and Technology 404
Concentration in ppm
The concentration of a solution is defined as the amount of solute in a given amount of
solution. It can be expressed as g/L, % or ppm (parts per million).
When the amount of solute is very small, we use ppm to express concentration. It is often
used to express concentrations of substances in the atmosphere, in water and in the soil.
Formula for aqueous solutions
Formula for non-aqueous solutions
1 ppm = 1 g of solute per 1 000 000 ml of solution
1 ppm = 1 g of solute per 1 000 000 g
or
1 ppm = 1 ml of solute per 1 000 000 ml
Converting units:
1 g = 1000 mg
1 kg = 1000 g
1 L = 1000 ml
Questions:
Problems involving aqueous solutions:
1. The water in a lake is contaminated. A technician takes 100 ml of the lake water
and determines that the sample contains 5 mg of contaminant. Calculate the
concentration of the contaminant in the water in ppm.
2. Two samples of water have been mixed up. One contains pool water, the other, tap
water. When the water is tested, Bottle A is found to contain 0.03 mg of chlorine
in 75 ml of solution. Bottle B is found to contain 0.0001 g of chlorine in 100 ml of
solution. Which is the sample of pool water? The acceptable level of chlorine in
drinking water is 0.5 ppm.
3. Water that has more than 50 ppm of minerals in it is considered hard water. Are
the following samples hard water or soft water?
a) 40 mg in 1000 ml
b) 0.06 g in 1 L
c) 2.5 mg in 200 ml
d) 0.015 g in 500 ml
e) 25 mg in 250 ml
4. Phosphates can lead to increased plant growth and large quantities of phosphates
will lead plants to grow out of control. Phosphate levels should not be higher than
0.03 ppm. A water sample from a pond was found to contain 0.0002 mg in 10ml of
water. Do you expect to see increased plant growth (algae) in that pond?
5. Nitrates are the main components of fertilizer and their run-off can enter our
streams and contaminate our drinking water. High nitrate levels can seriously harm
young children.
Water levels with greater than 40 ppm is deemed unsafe for human consumption. A
50 ml water sample was taken from a stream located near a golf club and tested. It
was found to contain 0.003 g of phosphate. Is the water potable?
6. The label on a 355 ml coke can reads that there is there is 141 ppm of sodium in it.
A) How many milligrams of sodium are in the can of coke?
B) What is the concentration of sodium in %?
C) What is the concentration of sodium in g/L?
7. The label on a bottle of water states that the water contains 28 ppm of magnesium.
a) What is the concentration in g/L?
b) What is the concentration in %?
8. A residential pool contains 100 000 L of water. It requires a concentration of 3 ppm
of chlorine. How much solute (chlorine compound) in grams is needed in the pool?
Problems involving non-aqueous solutions:
9. The acceptable exposure level of mercury (Hg) is 2 ppm. A 30 g sample taken from
a waste dump has 0.10 mg of Hg in it. Is this level acceptable?
10. Good quality soil contains at least 500 ppm of zinc (Zn). A 0.05 kg soil sample taken
from an industrial section of town was found to contain 0.02 g of zinc. Is this good
quality soil?
11. Concentrations of cadmium (Cd) in a soil sample was eight times higher than that
prescribed by the authorities. A 1 kg sample of soil was found to contain 0.04 g of
cadmium. What is the acceptable level of cadmium?
12. You are told that the acceptable level of a particular contaminant is 20 ppm. Which
of the following samples would be considered acceptable?
a) 0.04 g/L
b) 0.001 %
1. The water in a lake is contaminated. A technician takes 100 ml of the lake water
and determines that the sample contains 5 mg of contaminant. Calculate the
concentration of the contaminant in the water in ppm.
5 mg = 0.005 g
0.005g
x
100 ml =
1 000 000 ml
= 50 ppm
2. Two samples of water have been mixed up. One contains pool water, the other, tap
water. When the water is tested, Bottle A is found to contain 0.03 mg of chlorine
in 75 ml of solution. Bottle B is found to contain 0.0001 g of chlorine in 100 ml of
solution. Which is the sample of pool water? The acceptable level of chlorine in
drinking water is 0.5 ppm.
0.03 mg = 0.00003 g
Bottle A0.00003 mg
75 ml
x
=
Bottle B 0.0001 g
1 000 000 ml
100 ml =
x
1 000 000ml
= 0.4 ppm
= 1 ppm
3. Water that has more than 50 ppm of minerals in it is considered hard water. Are
the following samples hard water or soft water?
a) 40 mg in 1000 ml
40 mg = 0.04 g =
1000 ml
x
1 000 000 ml =
40 ppm
SOFT
b) 0.06 g in 1 L
= 0.06 g =
x
1000 ml
1 000 000 ml = 60 ppm
HARD
c) 2.5 mg in 200 ml 2.5 mg =
0.0025 g
200 ml
=
x
1 000 000 ml = 12.5 ppm
SOFT
d) 0.015 g in 500 ml
= 0.015 g
x
500 ml =
1 000 000 ml = 30 ppm
e) 25 mg in 250 ml 25 mg = 0.025 g
250 ml =
SOFT
x
1 000 000 ml = 100 ppm
HARD
4. Phosphates can lead to increased plant growth and large quantities of phosphates
will lead plants to grow out of control. Phosphate levels should not be higher than
0.03 ppm. A water sample from a pond was found to contain 0.0002 mg in 10ml of
water. Do you expect to see increased plant growth (algae) in that pond?
0.0002 mg = 0.0000002 g
0.0000002 g
10 ml =
x
1 000 000 ml
= 0.02 ppm
NO ALGAE
5. Nitrates are the main components of fertilizer and their run-off can enter our
streams and contaminate our drinking water. High nitrate levels can seriously harm
young children.
Water levels with greater than 40 ppm is deemed unsafe for human consumption. A
50 ml water sample was taken from a stream located near a golf club and tested. It
was found to contain 0.003 g of phosphate. Is the water potable?
0.003 g =
x
50 ml
1 000 000 ml = 60 ppm
NOT POTABLE
6. The label on a 355 ml coke can reads that there is there is 141 ppm of sodium in it.
A) How many milligrams of sodium are is in the can of coke?
x
141 g
355 ml =
1 000 000 ml = 0.05 g = 50 mg of sodium
B) What is the concentration of sodium in %?
141 g
x
1 000 000 ml =
100 ml
= 0.014 %
C) What is the concentration of sodium in g/L?
141 g
x
1 000 000 ml =
1000 ml
= 0.141 g/L
7. The label on a bottle of water states that the water contains 28 ppm of magnesium.
a) What is the concentration in g/L?
X
28 g
1000 ml =
1 000 000 ml
= 0.028 g/L
b) What is the concentration in %?
X
28 g
100 ml =
1 000 000 ml
= 0.0028 %
8. A residential pool contains 100 000 L of water. It requires a concentration of 3 ppm
of chlorine. How much solute (chlorine compound) in grams is needed in the pool?
100 000 L = 100 000 000 ml
x
100 000 000 ml
3g
1 000 000 ml
= 300 g
Problems involving non-aqueous solutions:
9. The acceptable exposure level of mercury (Hg) is 2 ppm. A 30 g sample taken from
a waste dump has 0.10 mg of Hg in it. Is this level acceptable?
30 g = 30 000 mg
0.1 mg
You can also change both to g
30 000 mg
x
=
1 000 000 mg = 3.33 ppm
(too high)
10. Good quality soil contains at least 500 ppm of zinc (Zn). A 0.05 kg soil sample taken
from an industrial section of town was found to contain 0.02 g of zinc. Is this good
quality soil?
0.05 kg = 50 g
0.02 g
50 g
x
=
1 000 000 g = 400 ppm (too low, not good qual)
11. Concentrations of cadmium (Cd) in a soil sample was eight times higher than that
prescribed by the authorities. A 1 kg sample of soil was found to contain 0.04 g of
cadmium. What is the acceptable level of cadmium?
1 kg = 1000 g
0.04 g
x
1000 g
1 000 000 g = 40 ppm
Since it is 8 times higher, the acceptable level is 40 ppm ÷ 8 = 5 ppm
12. You are told that the acceptable level of a particular contaminant is 20 ppm.
Which of the following samples would be considered acceptable?
a)
b)
0.04 g/L
0.001 %
0.04 g
x
1000 ml =
1 000 000 ml = 40 ppm
0.001 g
x
100 ml =
1 000 000 ml = 10 ppm
Not acceptable
Acceptable